Description: Of the 600,000 stroke survivors per year, only 5% regain full control of the upper extremities (UE), resulting in many with residual deficits that persistently affect function. Hence, the overall long-term objective of this research program is to understand the principles and mechanisms underlying UE stroke rehabilitation and to provide a scientific basis for planning treatments for this population. In this proposed study, we establish the efficacy of a novel repetitive bilateral arm training with rhythmic auditory cueing protocol for patients with chronic UE hemiparesis. This protocol is simple and applicable to a wide range of disability. We will undertake a randomized, controlled study with 72 patients (36 per group) comparing our training with dose-equivalent conventional OT/PT and measuring CNS changes. We hypothesize that 6 weeks of bilateral arm training with rhythmic auditory cueing (BATRAC) will durably improve function in patients with chronic UE hemiparesis through mechanisms mediated by changes in CNS structure and function. Specific aims are 1. To determine the effects of 6 weeks of repetitive BATRAC compared to 6 weeks of dose-equivalent conventional OT/PT in reversing UE functional disability. 1a: Does 6 weeks BATRAC improve UE motor function as demonstrated by changes in laboratory-based tests of motor impairment, functional ability, motor control, strength and range of motion? 1 b: Does 6 weeks BATRAC improve home/community-based assessment of UE daily use and quality of life scales? 2. To examine the mechanisms underlying adaptations to repetitive BATRAC by measuring UE CNS structure and function. 2a. Does 6 weeks BATRAC show a change in volume and location of movement-activated cortical tissue as determined fMRI? 2b. Does 6 weeks BATRAC show an improvement of CNS excitability through the assessment of TMS cortical stimulation threshold, location and motor evoked potentials? 3. To determine the durability of 6-weeks repetitive BATRAC by re-testing after 6 months without further formal training. 3a. Does 6 weeks BATRAC show a maintained improvement in UE motor function 6 months later? 3b. Does 6 weeks BATRAC show a maintained improvement in UE daily use and quality of life 6 months later? Accomplishment of these aims will uncover mechanistic principals underlying repetitive rhythmic bilateral training and provide the foundation for an effective and broadly applicable training program that would benefit the increasing number of patients with chronic UE deficits after stroke.